1. Field of the Invention
The present invention relates generally to air filter systems for small internal combustion engines, and more specifically, to an air filter assembly for filtering air prior to the air entering the carburetor.
2. Description of the Related Art
The filtering of air prior to combustion is necessary to maintain an internal combustion engine in a satisfactory condition. Two of the more common air cleaning methods, often used in conjunction, are subjecting the airflow to abrupt changes in direction, which utilizes the forward inertia of the larger particulates to remove them from the continuing path of the airflow and filtering the airflow through one or more filter media.
In many small engines, such as those used with lawnmowers and other similar machinery, the air for combustion is withdrawn from the engine's blower housing by a conduit or duct leading to the air cleaner housing. Generally, once the air exits the blower housing and enters this duct, the heavier particulates which are removed from the airflow, due to abrupt changes in the direction of the airflow, are maintained internally within the duct and air cleaner housing. These heavier particulates accumulate within the housing and upon the air filter. The accumulation of particulates upon the air filter clogs or hinders the required airflow to the carburetor and necessitates the periodic replacement or cleaning of the air filter. It is also possible for worn or clogged filters to allow particulates to enter the engine where the particulates can produce detrimental wear due to their abrasive effects.
One approach to deterring the accumulated particulates from entering the engine is to provide a second filter, made of felt, for example, immediately downstream of a first filter which can be made of a polyurethane foam. When the first filter begins releasing particulates due to their excessive accumulation, the second filter traps and thereby prevents the particulates from entering the engine.
Another approach that has been taken to deter particulates from entering the engine is to reduce the amount of debris and particulates which initially enter the blower housing. This is often done by using a rotating screen which is placed over the air intake port and rotates along with the engine cooling fan. Much of the foreign matter that approaches the air intake port is flung away by the rotating screen. A stationary filtering device can also be placed over the air intake port to filter out much of the debris and particulates from the air before it enters the blower housing. A hole may also be placed in the blower housing to allow for the discharge of particulates separated from the air stream by the centrifugal forces generated by the blower.
None of these approaches, however, provides for the discharge of accumulated debris and particulates once they have entered the air cleaner duct or housing. The accumulation of debris and particulates within the air cleaner system can be particularly troublesome for small internal combustion engines for use with tillers, chipper/shredders, generators, snow blowers, water pumps, pressure washers, leaf blowers, vacuums, sweepers, log splitters, core pluggers, stump cutters, trenchers, thatchers, power rakes, sod cutters, lawn mowers, lawn rollers, two-wheel tractors, go-karts, mini-bikes, and other similar machinery which are often exposed to air containing a large quantity of particulates such as dirt, grass clippings and matted debris.